Heat exchanger



NOV `22, 1949 c. D. MaccRAcKEN HEAT EXCHANGER 2 Sheets-Sheety l Filed March 1', 1947 Nov. 22, 1949 Filed March l, 1947 f c. D. MaocRAcKEN 2,488,549

HEAT EXCHANGER 2 Shee'ts-Sheet-Z INVENTOR. @a V//v .Q /746' P4C/av ing one way i Patented Nov. 22, 1949 HEAT EXCHANGER calvin D. Muenchen, New irachene. N. Y., as-

`signor, by direct and mesne assignments, to

Jet-Heet, Inc., New York, N.

of New York Y., a corporation Application March 1, 1947, Serial No. 731,831

4 Claims.

This invention relates to heat exchangers for many purposes, but particularly for usein ahouseheating or air-conditioning apparatus. The general object of the invention is to provide a heat .exchanger which is simple and compact in construction, easily manufactured, adaptable to rapid temperature change, low in heat storage, and highly eicient in operation. The embodiments of the invention hereinafter described and illustrated are particularly useful for the heating of air by the gaseous products of combustion from a fuel burner.

rAs will hereafter appear, in all of these embodiments of the invention, the internal construction of the heat exchanger is such that the air to be heated and the heating gases pass respectively in opposite spiral paths through the heat exchanger. Moreover, the internal construction of the heat exchanger is such that the crosssectional area of the passage traversed by the air being heated constantly increases in the direction of air flow; and the cross-sectional area of the passage traversed by the heating gases constantly decreases in the direction of gas ow. 'Ihis is an advantageous arrangement, because it maintainsl essentially constant the velocities of the air ilow and the gas ilow, and produces a maximum heat 'transfer with a given surface area with Va minimum pressure drop in the air and the heating gases.

through theY ribbon-like hollow member shown in Fig. 1 through whichthe hot gases pass, illustratm which the metal sheets forming that member may be joined at their edges; Fig. 3 is an end elevation, with the right-hand end wall of the heat exchanger and the end closure .plate of Fig. 1 removed, showing how the hollow ribbon-like member which carries the hot gases is spirally arranged within the casing of the heat exchanger; Fig. 4 is a fragmentary sectional view,

' similar to Fig. 2, showing another way in which the edges of the metal sheets forming the hollow member may be joined together at their edges; and Fig. 5 is a fragmentary sectional view showing still another way in which said sheets may be joined at their edges. p

Referring particularly to Figs. 1, 2 and 3, it will be evident that the heat exchanger therein illustrated comprises a housing enclosing an. annular space, formed by concentrically arranged outer and inner sheet-metal cylindricalshells III and I2, and end walls I4 and. I6 also of sheet metal cooperating with said shells. For example, the shells I0 and I2 may be made of sheet metal having a thickness of about 0.03 of an inch; and the end walls I4 and I6 may be made of sheet metal having a thickness of about 0.06 of an inch. The end wall I4 provides, between its outside edge and the shell III, an annular opening I3, airflow therethrough being indicated by the arrows a, through which the air to be heated enters the housing; and the other end wall I6 provides, between its inner edge and the inner shell I2, an annular opening I5, airflow therethrough being indicated by the -arrows b, through which the heated air leaves the housing and enters an annular chamber 22 from which it may be distributed in any desired way, -as by the pipes 24 connected to said annular chamber 22, out of which the heated air passes as indicated by the arrows c. Chamber 22 has an end closure plate 23. It will alsobe noted that the inner shell I2 and outer shell I0, respectively, are provided with openings through which project the necks 26 and 2'I through which the heated gases enter and leave the hollow member or heating element (hereinafter described) which is located Within the housing.

In all of the forms of the invention illustrated, the ribbon-like hollow heating element (hereinafter described) through which the heating gases pass is arranged in a spiral in the annular space within the housing, and the edges of said heating element are in free sliding engagement with the end walls Il and I 6. This heating element is preferably made of stainless steel in the form of strips or sheets having a thickness of, for example, about 0.02 of an inch. Many means may be provided for insuring that the hollow heating element will be retained in the desired spiral form. For example, as shown in Figs. 1 and 3, spacing blocks 28 and 29 are secured to the inner sides of the end Walls I4 and I6, and cooperate with the `edges of the hollow heating element. These spacwithout warping or distortion. This is an important advantage of applicants heat exchanger. Another advantage of applicants heat exchanger results from the fact that, since the hollow heating element and the concentrically arranged shells within which it is housed are made of thin sheet metal, the heat-storage capacity of the heat exchanger is low and temperature changes can take place rapidly. Thus, when called upon to do so, the heat exchanger will very quickly supply heated air at the desired temperature.

It will be evident that the hollow heating element not only provides a passage for the heating gases, but also serves as a spiral partition within the housing; and by reason of that fact the hot gases and the air to be heated pass in opposite directions in spiral paths through the heat exchanger. Morover, as will be hereafter explained, the hollow heating element is so constructed and arranged that the spiral path for the heating gases gradually decreases in cross-sectional area from the entrance end to the delivery end, and the spiral path for the air to be heated gradually increases in cross-sectional area from the entrance end to the delivery end. When the air to be heated enters the housing through the annular opening I3 as indicated by the arrows a. it comes first into contact with the outer and cooler portion of the hollow spiral partition, and as the air proceeds through the spiral space dened by that partition and the end walls I4 and I6 its temperature is raised by contact with hotter and hotter portions of the hollow spiral partition, until the hot air passes through the annular opening I5 as indicated by the arrows b into the annular space 22 from which it is distributed through the pipes 24.

'Ihe construction and arrangement of the hollow heating element, which is spirally arranged in the annular space betweenthe outer and inner shells I0 and I2 and the end walls I4 and I6, will be apparent from Figs. 1, 2 and 3. As shown in those ilgures, the heating element consists of metal sheets 34 and 36, preferably of stainless steel, formed as shown and welded together at their edges 38 and 40 as indicated at 42 in Fig. 2., As hereinbefore mentioned, the edges 38 and 40 are in free sliding engagement with the end walls I4 and I6 and with the spacing blocks 28 or 29; and the hollow heating element serves as a spiral partition within the housing. At their ends, the metal sheets 34 and 36 are pinched together and welded to one another as shown at 44 and 46 in Fig. 3. From Figs. 1 and 3 it will also be noted that the hollow heating element is so constructed and arranged in a spiral that the cross-sectional area of the path within the heating element gradually decreases from the inner end of the spiral to the outer end thereof, and so that the cross-sectional area of the spiral path between the convolutions of the spiral gradually increases from the outer to the inner end thereof. The advantages of this construction have been hereinbefore mentioned. As will be obvious from Figs. 1 and 3, the inner end of the spirally arranged hollow heating element is provided with an outlet opening in the form of a pipe 26 which extends through the opening in the inner shell I2; and near its outer end said hollow heating element is provided with a pipe 21 which extends through the opening in the outer shell III. However, the important fact is that the spirally arranged hollow heating element is provided near its inner and outer ends. respectively. with an opening which is located in alignment with an opening in said inner and outer shells I2 and I0. respectively; and the details of construction at these points may be modified without departing from the spirit of the invention.

In Figs. 1 and 3, the direction of ow of the heating gases where they enter the hollow heating element is indicated by the arrow d; and the direction of iiow of those gases where they leave the hollow heating element is indicated by the arrow e. In Fig. 3 the direction of ilow of the heating gases, within the spirally arranged hollow heating element, is indicated by the arrows f as being in a clockwise direction; and

` the direction of how of the air to be heated, in the spiral space provided between the outer and inner shells I0 and I2 and between the convolutions of the hollow heating member, is indicated by the arrows g as being in a counter-clockwise direction. Thus it will be apparent that the air to be heated and the hot gases which supply the heat pass, respectively, in opposite spiral paths through the heat exchanger. The advantages resulting from this flowing of the heating gases and the air to be heated have been hereinbefore mentioned.

Fig. 4 shows another construction of the Vhollow heating element which is also preferably made of stainless steel. As shown in this figure, the heating 'element may consist of a at metal sheet 50, and a metal sheet 52 which is oiset at its edges 54 by gradually decreasing amounts from the inner end tothe outer end of the spiral. The edge 56 of the sheet 50 is welded to the edge 54 of the sheet 52 as indicated at 58. As in case of the hollow heating element shown in Figs. l, 2 and 3, the sheets 50 and 52 are pinched together and welded to one another at their ends, in the manner indicated at 44 and 46 in Fig. 3.

Fig. 5 illustrates still another way in which the edges of the thin stainless steel sheets forming the ribbon-like hollow heating element may be joined together at their edges. As shown in Fig. 5, the hollow heating member comprises the spaced-apart thin metal sheets 60 and 62 and a bridging member 64 also of stainless steel which is U-shaped in cross section and is interposed between the edges of said sheets 60 and 82 and is welded thereto as indicated at 66 and 68. The U-shaped bridging member 64 is so made that it gradually decreases in width where it is interposed between the edges of the sheets 60 and 62, thereby gradually decreasing the crosssectional area of the' space within the hollow heating element from the outer part to the inner part of the spiral in which said heating element is arranged. As in the case of the hollow heating elements previously described, the sheets 60 and 62 at their ends are pinched together and welded to one another in the manner indicated at 44 and 46 in Fig. 3. It will be understood that the edges of the hollow heating elements illustrated in Figs. 4 and 5 are in free sliding engagement with end walls I4 and I6 of the housing and cooperate with suitable spacing means such as the blocks 28 and 28, in the manner indicated in Fig. 1 and hereinbefore described. Of course, the ribbon-like hollow heating element may be constructed in other ways without departing from the spirit of the invention, and without sacriilcing the advantages of the constructions and spiral arrangement of the hollow heating element which have been described.

What is claimed is:

1. A heat exchanger'comprising an outer shell, an innershell arranged within and spaced from said outer shell, end walls extending across the spaces between said inner and outer shells thereby providing a chamber between said shells, one

Iof said end walls having its periphery spaced from said outer shell to provide an opening around its outer edge and Vthe other end wall having its inner edge spaced from said inner shell to provide an opening around its inner edge, a hollow ribbon-like heating element spirally arranged in said chamber with its edges slidably positioned adjacent said end walls thus providing internally a spiral path for heated fluid and externally in said chamber a second spiral path for fluid to be heated, said heating element having inlet and outlet openings for hot uid, whereby heat exchange is provided for between the hot fluid passing through said heating element and fluid to be heated passing through said end wall openings and said second spiral path.

2. A heat exchanger comprising an outer shell, an inner shell arranged within and spaced from said outer shell, end walls extending across the spaces between said inner and outer shells thereby providing a chamber between vsaid shells, one of said end walls having its periphery spaced from said outer shell to provide an opening around its outer edge and the other end wall having its inner edge spaced from said inner shell to provide an opening around its inner edge, a hollow ribbon-like heating element spirally arranged in said chamber so as to be spaced from said inner and outer shells and with its edges slidably positioned adjacent said end walls thus providing internally a spiral path for heated fluid l and externally in said chamber a second spiral path for fluid to be heated, the space around the periphery of one of said end walls communicating with the space between said heating element and said outer shell and the space around theinner edge of the other of said end walls communicating with the space between said heating element and said inner shell, said heating element having inletand outlet openings for hot fluid, whereby heat exchange is provided for between the hot fluid passing through said heating element and :duid to be heated passing through the openings around said end walls and said second spiral path.

3. A heat exchanger comprising an outer shell, an inner shell arranged within and spaced from said outer shell, spaced apart end walls extending slidably positioned adjacent saidl end walls, said across the space between said inner and outer shells thereby providing a chamber between the shells, a hollow ribbon-like heating element spirally arranged in said chamber with its edges heating element having inlet and outlet openings for hot iiuid thus providing internally a spiral path for heated fluid and externally in said chamber .a' second spiral path for fluid to be heated, one of said end walls having a gas passage disposed around its outer edge and communicating with the space between said heating element and said outer shell and the other of said end walls having a gas passage disposed around its inner edge and communicating with the space between said heating element and said inner shell, whereby heat exchange is provided for between the hot uid'passing through said heating -element and iiuid to be heated passing through said end wall gas passages and said second spiral path.

4. A heat exchanger comprising an outer shell, an inner shell arranged within and spaced from said outer shell, spaced apart end walls extending across the space between said inner and outer shells thereby providing a chamber between the shells, a hollow ribbon-like heating element spirally arranged in said chamber with its edges slidably positioned adjacent said end Walls, said heating element having an inlet opening for hot fluid at its inner end and an outlet opening at its outer end thus providing internally a spiral pathfor heated uid and externally in said chamber a second spiral path for fluid to be heated, one of said end walls having an inlet gas passage disposed around its outer edge and communicating with the space between said heating element and said outer shell and the other of said end walls having an outlet gas passage disposed around its inner edge and communicating with the space between said heating element and said inner shell, whereby heat exchange is provided for between the hot fluid passing outwardly through said heating element and fluid to be heated passing in counterow relation through said end wall gas passages and said second spiral path.

CALVIN D. MACCRACKEN.

REFERENCES -CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 1,833,664 Vandegrift Nov. 24, 1931 2,129,300 Bichowsky Sept. 6, 1938 2,236,976 Rosenblad Apr. 1, 1941 FOREIGN PATENTS' Number Country Date 3,027 Great Britain Dec. 10, 1860 of 1860 

